Call Canon 1 (800) 652-2666. If it is brand new and it is from a real Canon USA dealer, Canon will get it right. If you are buying grey .......... well you'er on your own.

BTW, it is unlikely the contacts (other lenses work OK) but if you must clean them use a q-tip and denatured alcohol. Nothing else!

Someone with more knowledge of chemistry than I have may want to weigh in on this, but I'd be inclined to prefer isopropyl alcohol over denatured alcohol, precisely because it's already poisonous and therefore doesn't need to be "denatured" (in order to prevent it from turning up in untaxed liquor). The whole point of using alcohol to clean contacts is that in its pure form it doesn't leave a residue. By definition, denatured alcohol contains an adulterant; and depending on what that adulterant is, it might conceivably leave a residue.

Denatured alcohol is "denatured" usually by adding methanol to ethyl alcohol making it poisonous but having minor alteration on its prosperities.

Re: Problem with two different Canon 85mm f/1.8 Lenses

Denatured alcohol has always been the goto solvent for removing grime from hard surfaces, appliances, machinery, finished products and lens contacts. It is my preferred agent although I am sure others will work.

However, I still maintain cleaning the lens contacts is a rarely needed exercise. But if you must, denatured alcohol is a highly effective solvent and cleaning agent.

Re: Problem with two different Canon 85mm f/1.8 Lenses

The response from Canon Service is that there is "no Service Advisory for this lens". I'm out of luck to get it repaired for no cost_ I figured that would be a long shot. When I get it back, I will use it to make sure all functions are satisfactory. I like this lens for shooting indoor sports in poorly lit gyms, particularly volleyball. The picture quality is on par with my 70-200 f/2.8 II for this purpose, and it's 2/3 stop faster, and more hand holdable. I heavily crop final pictures and have been pleased with results. Let the testing begin.

Re: Problem with two different Canon 85mm f/1.8 Lenses... Power Diaphragm

Service and repair has been completed, and I have received the repaired lens.

The Service Details: "...it was found that the power diaphragm assembly was broken causing an error to be displayed from time to time. The power diaphragm was replaced. The product functions were confirmed."

I have no knowledge how or why this part broke, and it is not a lens that I heavily use, but I have done some test shots, and it appears that it actually locks on focus faster than what I remember before the repair, so that's all good. Canon Service turnaround time was very good, as it took only 5 days from the time it was sent in until is was returned back to me. That is based on me living in Norcal and the repairs done in Socal. Hopefully, this issue is closed for me.

Re: Problem with two different Canon 85mm f/1.8 Lenses... Power Diaphragm

My issue with this, is that it is happening just on the 85mm f/1.8 lens. I have other lenses that don't do this. I got a similar response from Canon, but am taking additional steps. If they stand behind their gear, then this problem should not happen just on a specific lens.